Difference between revisions of "Venn diagram"

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[[File:Venn diagram gr la ru.svg|thumb|'''Venn diagram''' showing which uppercase letter [[glyph]]s are shared by the [[Greek alphabet|Greek]], [[ISO basic Latin alphabet|Latin]] and [[Russian alphabet|Russian]] alphabets]]
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[[File:Venn diagram gr la ru.svg|thumb|'''Venn diagram''' showing which uppercase letter [[glyph]]s are shared by the [[Greek alphabet|Greek]], [[Latin alphabets|Latin]] and [[Cyrillic script|Cyrillic]] alphabets]]
 
{{Probability fundamentals}}
 
{{Probability fundamentals}}
A '''Venn diagram''' or '''set diagram''' is a [[diagram]] that shows all possible [[logic]]al relations between a finite collection of [[Set (mathematics)|sets]]. Venn diagrams were conceived around 1880 by [[John Venn]]. They are used to teach elementary [[set theory]], as well as illustrate simple set relationships in [[probability]], [[logic]], [[statistics]], [[linguistics]] and [[computer science]].
+
A '''Venn diagram''' or '''set diagram''' is a [[diagram]] that shows all possible [[logic]]al relations between a finite collection of different [[Set (mathematics)|sets]]. Venn diagrams were conceived around 1880 by [[John Venn]]. They are used to teach elementary [[set theory]], as well as illustrate simple set relationships in [[probability]], [[logic]], [[statistics]], [[linguistics]] and [[computer science]].
  
== Example ==
+
==Example==
 
[[Image:venn-diagram-AB.svg|thumb|left|Sets A (creatures with two legs) and B (creatures that can fly)]]
 
[[Image:venn-diagram-AB.svg|thumb|left|Sets A (creatures with two legs) and B (creatures that can fly)]]
 
This example involves two [[Set (mathematics)|sets]], A and B, represented here as coloured circles. The orange circle, set A, represents all living creatures that are two-legged. The blue circle, set B, represents the living creatures that can fly. Each separate type of creature can be imagined as a point somewhere in the diagram.  Living creatures that both can fly ''and'' have two legs—for example, parrots—are then in both sets, so they correspond to points in the area where the blue and orange circles overlap. That area contains all such and only such living creatures.
 
This example involves two [[Set (mathematics)|sets]], A and B, represented here as coloured circles. The orange circle, set A, represents all living creatures that are two-legged. The blue circle, set B, represents the living creatures that can fly. Each separate type of creature can be imagined as a point somewhere in the diagram.  Living creatures that both can fly ''and'' have two legs—for example, parrots—are then in both sets, so they correspond to points in the area where the blue and orange circles overlap. That area contains all such and only such living creatures.
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The area in both A and B, where the two sets overlap, is called the ''[[intersection (set theory)|intersection]]'' of A and B, denoted by {{nowrap|A ∩ B}}. For example, the intersection of the two sets is not empty, because there ''are'' points that represent creatures that are in ''both'' the orange and blue circles.
 
The area in both A and B, where the two sets overlap, is called the ''[[intersection (set theory)|intersection]]'' of A and B, denoted by {{nowrap|A ∩ B}}. For example, the intersection of the two sets is not empty, because there ''are'' points that represent creatures that are in ''both'' the orange and blue circles.
  
== History ==
+
==History==
Venn diagrams were introduced in 1880 by [[John Venn]] (1834–1923) in a paper entitled ''On the Diagrammatic and Mechanical Representation of Propositions and Reasonings'' in the "Philosophical Magazine and Journal of Science", about the different ways to represent [[proposition]]s by diagrams.<ref name=Sandifer2003/> The use of these types of [[diagram]]s in [[formal logic]], according to Ruskey and M. Weston, is "not an easy history to trace, but it is certain that the diagrams that are popularly associated with Venn, in fact, originated much earlier. They are rightly associated with Venn, however, because he comprehensively surveyed and formalized their usage, and was the first to generalize them".<ref name=Ruskey2005/>
+
Venn diagrams were introduced in 1880 by [[John Venn]] (1834–1923) in a paper entitled ''On the Diagrammatic and Mechanical Representation of Propositions and Reasonings'' in the "Philosophical Magazine and Journal of Science", about the different ways to represent [[proposition]]s by diagrams.<ref name=Venn1880/><ref name=Sandifer2003/> The use of these types of [[diagram]]s in [[formal logic]], according to Ruskey and M. Weston, is "not an easy history to trace, but it is certain that the diagrams that are popularly associated with Venn, in fact, originated much earlier. They are rightly associated with Venn, however, because he comprehensively surveyed and formalized their usage, and was the first to generalize them".<ref name=Ruskey2005/>
  
 
Venn himself did not use the term "Venn diagram" and referred to his invention as "Eulerian Circles."<ref name=Sandifer2003/> For example, in the opening sentence of his 1880 article Venn writes, "Schemes of diagrammatic representation have been so familiarly introduced into logical treatises during the last century or so, that many readers, even those who have made no professional study of logic, may be supposed to be acquainted with the general nature and object of such devices. Of these schemes one only, viz. that commonly called 'Eulerian circles,' has met with any general acceptance..."<ref name=Venn1880/> The first to use the term "Venn diagram" was [[Clarence Irving Lewis]] in 1918, in his book "A Survey of Symbolic Logic".<ref name=Ruskey2005/>
 
Venn himself did not use the term "Venn diagram" and referred to his invention as "Eulerian Circles."<ref name=Sandifer2003/> For example, in the opening sentence of his 1880 article Venn writes, "Schemes of diagrammatic representation have been so familiarly introduced into logical treatises during the last century or so, that many readers, even those who have made no professional study of logic, may be supposed to be acquainted with the general nature and object of such devices. Of these schemes one only, viz. that commonly called 'Eulerian circles,' has met with any general acceptance..."<ref name=Venn1880/> The first to use the term "Venn diagram" was [[Clarence Irving Lewis]] in 1918, in his book "A Survey of Symbolic Logic".<ref name=Ruskey2005/>
  
Venn diagrams are very similar to [[Euler diagram]]s, which were invented by [[Leonhard Euler]] (1708–1783) in the 18th century.<ref group=note>In Euler's ''Letters to a German Princess.'' In Venn's article, however, he suggests that the diagrammatic idea predates Euler, and is attributable to C. Weise or J. C. Lange.</ref> M.&nbsp;E.&nbsp;Baron has noted that [[Gottfried Wilhelm Leibniz|Leibniz]] (1646–1716) in the 17th century produced similar diagrams before Euler, but much of it was unpublished. She also observes even earlier Euler-like diagrams by [[Ramon Lull]] in the 13th Century.<ref>{{cite journal |author=Baron, M.E. |title=A Note on The Historical Development of Logic Diagrams |journal=[[The Mathematical Gazette]] |volume=53 |issue=384  |pages=113–125 |date=May 1969 |jstor=3614533 |doi=10.2307/3614533 }}</ref>
+
Venn diagrams are very similar to [[Euler diagram]]s, which were invented by [[Leonhard Euler]] (1708–1783) in the 18th century.<ref group=note>In Euler's ''Lettres à une princesse d'Allemagne sur divers sujets de physique et de philosophie'' [Letters to a German Princess on various physical and philosophical subjects] (Saint Petersburg, Russia:  l'Academie Impériale des Sciences, 1768), volume 2, [http://books.google.com/books?id=gxsAAAAAQAAJ&pg=PA95#v=onepage&q&f=false pages 95-126.]  In Venn's article, however, he suggests that the diagrammatic idea predates Euler, and is attributable to [[Christian Weise]] or Johann Christian Lange (in Lange's book ''Nucleus Logicae Weisianae'' (1712)).</ref> M.&nbsp;E.&nbsp;Baron has noted that [[Gottfried Wilhelm Leibniz|Leibniz]] (1646–1716) in the 17th century produced similar diagrams before Euler, but much of it was unpublished. She also observes even earlier Euler-like diagrams by [[Ramon Lull]] in the 13th Century.<ref>{{cite journal |author=Baron, M.E. |title=A Note on The Historical Development of Logic Diagrams |journal=[[The Mathematical Gazette]] |volume=53 |issue=384  |pages=113–125 |date=May 1969 |jstor=3614533 |doi=10.2307/3614533 }}</ref>
  
 
In the 20th century, Venn diagrams were further developed. D.W. Henderson showed in 1963 that the existence of an ''n''-Venn diagram with ''n''-fold [[rotational symmetry]] implied that ''n'' was a [[prime number]].<ref>{{cite journal |author=Henderson, D.W. |title=Venn diagrams for more than four classes |journal=[[American Mathematical Monthly]] |volume=70  |issue=4 |pages=424–6 |date=April 1963 |jstor=2311865 |doi=10.2307/2311865 }}</ref>  He also showed that such symmetric Venn diagrams exist when ''n'' is 5 or 7. In 2002 Peter Hamburger found symmetric Venn diagrams for ''n'' = 11 and in 2003, Griggs, Killian, and Savage showed that symmetric Venn diagrams exist for all other primes. Thus rotationally symmetric Venn diagrams exist if and only if ''n'' is a prime number.<ref>{{cite journal |last=Ruskey |first=Frank |first2=Carla D. |last2=Savage |authorlink2=Carla Savage|first3=Stan  |last3=Wagon |authorlink3=Stan Wagon |date=December 2006 |title=The Search for Simple Symmetric Venn Diagrams |journal=[[Notices of the AMS]] |volume=53 |issue=11 |pages=1304–11 |url=http://www.ams.org/notices/200611/fea-wagon.pdf | format = PDF}}</ref>
 
In the 20th century, Venn diagrams were further developed. D.W. Henderson showed in 1963 that the existence of an ''n''-Venn diagram with ''n''-fold [[rotational symmetry]] implied that ''n'' was a [[prime number]].<ref>{{cite journal |author=Henderson, D.W. |title=Venn diagrams for more than four classes |journal=[[American Mathematical Monthly]] |volume=70  |issue=4 |pages=424–6 |date=April 1963 |jstor=2311865 |doi=10.2307/2311865 }}</ref>  He also showed that such symmetric Venn diagrams exist when ''n'' is 5 or 7. In 2002 Peter Hamburger found symmetric Venn diagrams for ''n'' = 11 and in 2003, Griggs, Killian, and Savage showed that symmetric Venn diagrams exist for all other primes. Thus rotationally symmetric Venn diagrams exist if and only if ''n'' is a prime number.<ref>{{cite journal |last=Ruskey |first=Frank |first2=Carla D. |last2=Savage |authorlink2=Carla Savage|first3=Stan  |last3=Wagon |authorlink3=Stan Wagon |date=December 2006 |title=The Search for Simple Symmetric Venn Diagrams |journal=[[Notices of the AMS]] |volume=53 |issue=11 |pages=1304–11 |url=http://www.ams.org/notices/200611/fea-wagon.pdf | format = PDF}}</ref>
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Venn diagrams and Euler diagrams were incorporated as part of instruction in [[set theory]] as part of the [[new math]] movement in the 1960s. Since then, they have also been adopted by other curriculum fields such as reading.<ref>[http://www.readingquest.org/strat/venn.html Strategies for Reading Comprehension Venn Diagrams]</ref>
 
Venn diagrams and Euler diagrams were incorporated as part of instruction in [[set theory]] as part of the [[new math]] movement in the 1960s. Since then, they have also been adopted by other curriculum fields such as reading.<ref>[http://www.readingquest.org/strat/venn.html Strategies for Reading Comprehension Venn Diagrams]</ref>
  
== Overview ==
+
==Overview==
 
{{See also|Set (mathematics)#Basic operations}}
 
{{See also|Set (mathematics)#Basic operations}}
 
{{Gallery|lines=3
 
{{Gallery|lines=3
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|}
 
|}
  
For higher numbers of sets, some loss of symmetry in the diagrams is unavoidable. Venn was keen to find "symmetrical figures…elegant in themselves,"<ref name="Venn1881">{{cite book|author=Jo Venn|title=Symbolic logic|url=http://books.google.com/books?id=nisCAAAAQAAJ&pg=PA108|accessdate=9 April 2013|year=1881|publisher=Macmillan|page=108}}</ref> that represented higher numbers of sets, and he devised a four-set diagram using [[ellipse]]s (see below).  He also gave a construction for Venn diagrams for ''any'' number of sets, where each successive curve that delimits a set interleaves with previous curves, starting with the three-circle diagram.
+
For higher numbers of sets, some loss of symmetry in the diagrams is unavoidable. Venn was keen to find "symmetrical figures...elegant in themselves,"<ref name="Venn1881">{{cite book|author=John Venn|title=Symbolic logic|url=http://books.google.com/books?id=nisCAAAAQAAJ&pg=PA108|accessdate=9 April 2013|year=1881|publisher=Macmillan|page=108}}</ref> that represented higher numbers of sets, and he devised a four-set diagram using [[ellipse]]s (see below).  He also gave a construction for Venn diagrams for ''any'' number of sets, where each successive curve that delimits a set interleaves with previous curves, starting with the three-circle diagram.
  
 
<gallery widths=200px><!---perrow=3-->
 
<gallery widths=200px><!---perrow=3-->
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Image:Venn6.svg|Venn's construction for 6 sets
 
Image:Venn6.svg|Venn's construction for 6 sets
 
Image:Venn's four ellipse construction.svg|Venn's four-set diagram using ellipses
 
Image:Venn's four ellipse construction.svg|Venn's four-set diagram using ellipses
Image:CirclesN4xb.svg|'''Counter-example:''' This [[Euler diagram]] is '''not''' a Venn diagram for four sets as it has only 13 regions (excluding the outside); there is no region where only the yellow and blue, or only the pink and green circles meet.
+
Image:CirclesN4xb.svg|'''Non-example:''' This [[Euler diagram]] is '''not''' a Venn diagram for four sets as it has only 13 regions (excluding the outside); there is no region where only the yellow and blue, or only the red and green circles meet.
File:Symmetrical 5-set Venn diagram.svg|Five-set Venn diagram using congruent ellipses in a radially symmetrical arrangement devised by [[Branko Grünbaum]]. Labels have been simplified for greater readability; for example, '''A''' denotes '''A''' ∩ '''B'''<sup>c</sup> ∩ '''C'''<sup>c</sup> ∩ '''D'''<sup>c</sup> ∩ '''E'''<sup>c</sup>, while '''BCE''' denotes '''A'''<sup>c</sup> ∩ '''B''' ∩ '''C''' ∩ '''D'''<sup>c</sup> ∩ '''E'''.
+
File:Symmetrical 5-set Venn diagram.svg|Five-set Venn diagram using congruent ellipses in a 5-fold [[rotational symmetry|rotationally symmetrical]] arrangement devised by [[Branko Grünbaum]]. Labels have been simplified for greater readability; for example, '''A''' denotes '''A''' ∩ '''B'''<sup>c</sup> ∩ '''C'''<sup>c</sup> ∩ '''D'''<sup>c</sup> ∩ '''E'''<sup>c</sup>, while '''BCE''' denotes '''A'''<sup>c</sup> ∩ '''B''' ∩ '''C''' ∩ '''D'''<sup>c</sup> ∩ '''E'''.
 
File:6-set_Venn_diagram.svg|Six-set Venn diagram made of only triangles.
 
File:6-set_Venn_diagram.svg|Six-set Venn diagram made of only triangles.
 
</gallery>
 
</gallery>
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Edwards' Venn diagrams are [[Topological equivalence|topologically equivalent]] to diagrams devised by [[Branko Grünbaum]], which were based around intersecting [[polygon]]s with increasing numbers of sides. They are also 2-dimensional representations of [[hypercube]]s.
 
Edwards' Venn diagrams are [[Topological equivalence|topologically equivalent]] to diagrams devised by [[Branko Grünbaum]], which were based around intersecting [[polygon]]s with increasing numbers of sides. They are also 2-dimensional representations of [[hypercube]]s.
  
Smith{{Citation needed|date=January 2012}}  devised similar ''n''-set diagrams using [[sine]] curves with the series of equations
+
[[Henry John Stephen Smith]] devised similar ''n''-set diagrams using [[sine]] curves<ref>{{citation|title=Cogwheels of the Mind: The Story of Venn Diagrams|first=A. W. F.|last=Edwards|publisher=JHU Press|year=2004|isbn=9780801874345|page=65|url=http://books.google.com/books?id=7_0Thy4V3JIC&pg=PA65}}.</ref> with the series of equations
 
: <math>y_i = \frac {\sin(2^{i }x)}{2 i} \text{ where } 0 \leq i \leq n-2 \text{ and } i \in \mathbb{N}. </math>
 
: <math>y_i = \frac {\sin(2^{i }x)}{2 i} \text{ where } 0 \leq i \leq n-2 \text{ and } i \in \mathbb{N}. </math>
  
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==References==
 
==References==
 +
 
{{Reflist|refs=
 
{{Reflist|refs=
 
<ref name=Lewis1918>{{cite book|authorlink=Clarence Irving Lewis|first=Clarence Irving|last=Lewis|year=1918|url= http://www.archive.org/details/asurveyofsymboli00lewiuoft|title=A Survey of Symbolic Logic|location=Berkeley|publisher=University of California Press}}</ref>
 
<ref name=Lewis1918>{{cite book|authorlink=Clarence Irving Lewis|first=Clarence Irving|last=Lewis|year=1918|url= http://www.archive.org/details/asurveyofsymboli00lewiuoft|title=A Survey of Symbolic Logic|location=Berkeley|publisher=University of California Press}}</ref>
 +
 
<ref name=Sandifer2003>{{cite web|first=Ed|last=Sandifer|year=2003|title=How Euler Did It|url=http://www.maa.org/editorial/euler/How%20Euler%20Did%20It%2003%20Venn%20Diagrams.pdf|format=pdf|publisher=The Mathematical Association of America: MAA Online|accessdate=26 October 2009}}</ref>
 
<ref name=Sandifer2003>{{cite web|first=Ed|last=Sandifer|year=2003|title=How Euler Did It|url=http://www.maa.org/editorial/euler/How%20Euler%20Did%20It%2003%20Venn%20Diagrams.pdf|format=pdf|publisher=The Mathematical Association of America: MAA Online|accessdate=26 October 2009}}</ref>
 
<ref name=Ruskey2005>{{cite journal |author=Ruskey, F.; Weston, M. |title=Venn Diagram Survey |journal=The electronic journal of combinatorics  |date=June 2005 |url=http://www.combinatorics.org/Surveys/ds5/VennJohnEJC.html}}</ref>
 
<ref name=Ruskey2005>{{cite journal |author=Ruskey, F.; Weston, M. |title=Venn Diagram Survey |journal=The electronic journal of combinatorics  |date=June 2005 |url=http://www.combinatorics.org/Surveys/ds5/VennJohnEJC.html}}</ref>
<ref name=Venn1880>{{cite journal |author=Venn, J. |title=On the Diagrammatic and Mechanical Representation of Propositions and Reasonings |journal=Philosophical Magazine and Journal of Science |volume=10 |issue=59 |date=July 1880 |series=5}}</ref>
+
<ref name=Venn1880>See:
 +
*{{cite journal |author=Venn, J. |title=On the diagrammatic and mechanical representation of propositions and reasonings |journal=Philosophical Magazine and Journal of Science |volume=10 |issue=59 |date=July 1880 |series=5 | pages=1-18 | url = http://books.google.com/books?id=k68vAQAAIAAJ&pg=PA1#v=onepage&q&f=false }}
 +
*  John Venn (1880) [https://archive.org/stream/proceedingsofcam4188083camb#page/47/mode/1up "On the employment of geometrical diagrams for the sensible representations of logical propositions,"] ''Proceedings of the Cambridge Philosophical Society'', '''4''' :  47-59.</ref>
 
}}
 
}}
  
==Further reading ==
+
==Further reading==
 +
* [http://sharif.ir/~emahmood/papers/Generalized-Venn-Diagram1987.pdf Generalized Venn Diagrams 1987] by E. S. Mahmoodian, with M. Rezaie and F. Vatan.
 
* [http://www.combinatorics.org/Surveys/ds5/VennEJC.html A Survey of Venn Diagrams] by F. Ruskey and M. Weston, is an extensive site with much recent research and many beautiful figures.
 
* [http://www.combinatorics.org/Surveys/ds5/VennEJC.html A Survey of Venn Diagrams] by F. Ruskey and M. Weston, is an extensive site with much recent research and many beautiful figures.
 
*{{cite book |first=Ian  |last=Stewart |authorlink=Ian Stewart (mathematician) |chapter=Ch. 4 Cogwheels of the Mind |chapterurl=http://books.google.com.au/books?id=u5GPE97-ZhsC&pg=PA51 |title=Another Fine Math You've Got Me Into |publisher=Dover Publications  |year=2004 |isbn=0-486-43181-9 |pages=51–64}}
 
*{{cite book |first=Ian  |last=Stewart |authorlink=Ian Stewart (mathematician) |chapter=Ch. 4 Cogwheels of the Mind |chapterurl=http://books.google.com.au/books?id=u5GPE97-ZhsC&pg=PA51 |title=Another Fine Math You've Got Me Into |publisher=Dover Publications  |year=2004 |isbn=0-486-43181-9 |pages=51–64}}
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*{{Cite web |first=Khalegh |last=Ruskey |first2=Frank |last2=Ruskey |author2-link=Frank Ruskey |date=27 July 2012 |title=A New Rose : The First Simple Symmetric 11-Venn Diagram |arxiv=1207.6452 |url=http://webhome.cs.uvic.ca/~ruskey/Publications/Venn11/Venn11.html |bibcode=2012arXiv1207.6452M |volume=1207 |pages=6452 |postscript=<!-- Bot inserted parameter. Either remove it; or change its value to "." for the cite to end in a ".", as necessary. -->{{inconsistent citations}}}}
 
*{{Cite web |first=Khalegh |last=Ruskey |first2=Frank |last2=Ruskey |author2-link=Frank Ruskey |date=27 July 2012 |title=A New Rose : The First Simple Symmetric 11-Venn Diagram |arxiv=1207.6452 |url=http://webhome.cs.uvic.ca/~ruskey/Publications/Venn11/Venn11.html |bibcode=2012arXiv1207.6452M |volume=1207 |pages=6452 |postscript=<!-- Bot inserted parameter. Either remove it; or change its value to "." for the cite to end in a ".", as necessary. -->{{inconsistent citations}}}}
  
== External links ==
+
==External links==
 
{{Commons category|Venn diagrams}}
 
{{Commons category|Venn diagrams}}
 
* {{springer|title=Venn diagram|id=p/v096550}}
 
* {{springer|title=Venn diagram|id=p/v096550}}
 
* {{MathWorld |title=Venn Diagram |id=VennDiagram }}
 
* {{MathWorld |title=Venn Diagram |id=VennDiagram }}
* [http://www.eulerdiagrams.com/inductivecircles.html Free software for generating Venn and Euler diagrams using circles]
 
 
* [http://www.cut-the-knot.org/LewisCarroll/dunham.shtml Lewis Carroll's Logic Game – Venn vs. Euler] at [[cut-the-knot]]
 
* [http://www.cut-the-knot.org/LewisCarroll/dunham.shtml Lewis Carroll's Logic Game – Venn vs. Euler] at [[cut-the-knot]]
 
* [http://www.combinatorics.org/Surveys/ds5/VennEJC.html A Survey of Venn Diagrams]
 
* [http://www.combinatorics.org/Surveys/ds5/VennEJC.html A Survey of Venn Diagrams]
* [http://www.cs.kent.ac.uk/people/staff/pjr/EulerVennCircles/EulerVennApplet.html Area proportional 3-way venn diagram applet]
 
 
* [http://www.technomancy.org/google-suggest-venn/ Generating Venn Diagrams to explore Google Suggest results]
 
* [http://www.technomancy.org/google-suggest-venn/ Generating Venn Diagrams to explore Google Suggest results]
 
* [http://moebio.com/research/sevensets seven sets interactive Venn diagram displaying color combinations]
 
* [http://moebio.com/research/sevensets seven sets interactive Venn diagram displaying color combinations]
 
* [http://www.combinatorics.org/Surveys/ds5/VennTriangleEJC.html six sets Venn diagrams made from triangles]
 
* [http://www.combinatorics.org/Surveys/ds5/VennTriangleEJC.html six sets Venn diagrams made from triangles]
 
* [http://qandr.org/quentin/software/venn Postscript for 9-set Venn] and more
 
* [http://qandr.org/quentin/software/venn Postscript for 9-set Venn] and more
* [http://webdmamrl.er.usgs.gov/g1/FHWA/VBVenn/default.htm VBVenn – A Visual Basic program for calculating and graphing quantitative two-circle Venn diagrams]
+
 
{{logic}}
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{{Mathematical logic}}
 
{{Set theory}}
 
{{Set theory}}
  
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[[Category:Diagrams]]
 
[[Category:Diagrams]]
 
[[Category:Statistical charts and diagrams]]
 
[[Category:Statistical charts and diagrams]]
 
{{Link GA|es}}
 

Latest revision as of 15:32, 2 December 2014

Venn diagram showing which uppercase letter glyphs are shared by the Greek, Latin and Cyrillic alphabets

Template:Probability fundamentals A Venn diagram or set diagram is a diagram that shows all possible logical relations between a finite collection of different sets. Venn diagrams were conceived around 1880 by John Venn. They are used to teach elementary set theory, as well as illustrate simple set relationships in probability, logic, statistics, linguistics and computer science.

Example

File:Venn-diagram-AB.svg
Sets A (creatures with two legs) and B (creatures that can fly)

This example involves two sets, A and B, represented here as coloured circles. The orange circle, set A, represents all living creatures that are two-legged. The blue circle, set B, represents the living creatures that can fly. Each separate type of creature can be imagined as a point somewhere in the diagram. Living creatures that both can fly and have two legs—for example, parrots—are then in both sets, so they correspond to points in the area where the blue and orange circles overlap. That area contains all such and only such living creatures.

Humans and penguins are bipedal, and so are then in the orange circle, but since they cannot fly they appear in the left part of the orange circle, where it does not overlap with the blue circle. Mosquitoes have six legs, and fly, so the point for mosquitoes is in the part of the blue circle that does not overlap with the orange one. Creatures that are not two-legged and cannot fly (for example, whales and spiders) would all be represented by points outside both circles.

The combined area of sets A and B is called the union of A and B, denoted by A ∪ B. The union in this case contains all living creatures that are either two-legged or that can fly (or both).

The area in both A and B, where the two sets overlap, is called the intersection of A and B, denoted by A ∩ B. For example, the intersection of the two sets is not empty, because there are points that represent creatures that are in both the orange and blue circles.

History

Venn diagrams were introduced in 1880 by John Venn (1834–1923) in a paper entitled On the Diagrammatic and Mechanical Representation of Propositions and Reasonings in the "Philosophical Magazine and Journal of Science", about the different ways to represent propositions by diagrams.[1][2] The use of these types of diagrams in formal logic, according to Ruskey and M. Weston, is "not an easy history to trace, but it is certain that the diagrams that are popularly associated with Venn, in fact, originated much earlier. They are rightly associated with Venn, however, because he comprehensively surveyed and formalized their usage, and was the first to generalize them".[3]

Venn himself did not use the term "Venn diagram" and referred to his invention as "Eulerian Circles."[2] For example, in the opening sentence of his 1880 article Venn writes, "Schemes of diagrammatic representation have been so familiarly introduced into logical treatises during the last century or so, that many readers, even those who have made no professional study of logic, may be supposed to be acquainted with the general nature and object of such devices. Of these schemes one only, viz. that commonly called 'Eulerian circles,' has met with any general acceptance..."[1] The first to use the term "Venn diagram" was Clarence Irving Lewis in 1918, in his book "A Survey of Symbolic Logic".[3]

Venn diagrams are very similar to Euler diagrams, which were invented by Leonhard Euler (1708–1783) in the 18th century.[note 1] M. E. Baron has noted that Leibniz (1646–1716) in the 17th century produced similar diagrams before Euler, but much of it was unpublished. She also observes even earlier Euler-like diagrams by Ramon Lull in the 13th Century.[4]

In the 20th century, Venn diagrams were further developed. D.W. Henderson showed in 1963 that the existence of an n-Venn diagram with n-fold rotational symmetry implied that n was a prime number.[5] He also showed that such symmetric Venn diagrams exist when n is 5 or 7. In 2002 Peter Hamburger found symmetric Venn diagrams for n = 11 and in 2003, Griggs, Killian, and Savage showed that symmetric Venn diagrams exist for all other primes. Thus rotationally symmetric Venn diagrams exist if and only if n is a prime number.[6]

Venn diagrams and Euler diagrams were incorporated as part of instruction in set theory as part of the new math movement in the 1960s. Since then, they have also been adopted by other curriculum fields such as reading.[7]

Overview

{{#invoke:see also|seealso}} {{#invoke: Gallery | gallery}} A Venn diagram is constructed with a collection of simple closed curves drawn in a plane. According to Lewis,[8] the "principle of these diagrams is that classes [or sets] be represented by regions in such relation to one another that all the possible logical relations of these classes can be indicated in the same diagram. That is, the diagram initially leaves room for any possible relation of the classes, and the actual or given relation, can then be specified by indicating that some particular region is null or is not-null".[8]:157

Venn diagrams normally comprise overlapping circles. The interior of the circle symbolically represents the elements of the set, while the exterior represents elements that are not members of the set. For instance, in a two-set Venn diagram, one circle may represent the group of all wooden objects, while another circle may represent the set of all tables. The overlapping area or intersection would then represent the set of all wooden tables. Shapes other than circles can be employed as shown below by Venn's own higher set diagrams. Venn diagrams do not generally contain information on the relative or absolute sizes (cardinality) of sets; i.e. they are schematic diagrams.

Venn diagrams are similar to Euler diagrams. However, a Venn diagram for n component sets must contain all 2n hypothetically possible zones that correspond to some combination of inclusion or exclusion in each of the component sets. Euler diagrams contain only the actually possible zones in a given context. In Venn diagrams, a shaded zone may represent an empty zone, whereas in an Euler diagram the corresponding zone is missing from the diagram. For example, if one set represents dairy products and another cheeses, the Venn diagram contains a zone for cheeses that are not dairy products. Assuming that in the context cheese means some type of dairy product, the Euler diagram has the cheese zone entirely contained within the dairy-product zone—there is no zone for (non-existent) non-dairy cheese. This means that as the number of contours increases, Euler diagrams are typically less visually complex than the equivalent Venn diagram, particularly if the number of non-empty intersections is small.[9]

Extensions to higher numbers of sets

Venn diagrams typically represent two or three sets, but there are forms that allow for higher numbers. Shown below, four intersecting spheres form the highest order Venn diagram that has the symmetry of a simplex and can be visually represented. The 16 intersections correspond to the vertices of a tesseract (or the cells of a 16-cell respectively).

Venn 1000 0000 0000 0000.png Venn 0110 1000 1000 0000.png

Venn 0100 0000 0000 0000.pngVenn 0010 0000 0000 0000.pngVenn 0000 1000 0000 0000.pngVenn 0000 0000 1000 0000.png

Venn 0001 0110 0110 1000.png

Venn 0001 0000 0000 0000.pngVenn 0000 0100 0000 0000.pngVenn 0000 0010 0000 0000.pngVenn 0000 0000 0100 0000.pngVenn 0000 0000 0010 0000.pngVenn 0000 0000 0000 1000.png

Venn 0000 0001 0001 0110.png

Venn 0000 0001 0000 0000.pngVenn 0000 0000 0001 0000.pngVenn 0000 0000 0000 0100.pngVenn 0000 0000 0000 0010.png

Venn 0000 0000 0000 0001.png

For higher numbers of sets, some loss of symmetry in the diagrams is unavoidable. Venn was keen to find "symmetrical figures...elegant in themselves,"[10] that represented higher numbers of sets, and he devised a four-set diagram using ellipses (see below). He also gave a construction for Venn diagrams for any number of sets, where each successive curve that delimits a set interleaves with previous curves, starting with the three-circle diagram.

Edwards' Venn diagrams

A. W. F. Edwards constructed a series of Venn diagrams for higher numbers of sets by segmenting the surface of a sphere. For example, three sets can be easily represented by taking three hemispheres of the sphere at right angles (x = 0, y = 0 and z = 0). A fourth set can be added to the representation by taking a curve similar to the seam on a tennis ball, which winds up and down around the equator, and so on. The resulting sets can then be projected back to a plane to give cogwheel diagrams with increasing numbers of teeth, as shown on the right. These diagrams were devised while designing a stained-glass window in memory of Venn.

Other diagrams

Edwards' Venn diagrams are topologically equivalent to diagrams devised by Branko Grünbaum, which were based around intersecting polygons with increasing numbers of sides. They are also 2-dimensional representations of hypercubes.

Henry John Stephen Smith devised similar n-set diagrams using sine curves[11] with the series of equations

Charles Lutwidge Dodgson devised a five-set diagram.

Related concepts

Venn diagram as a truth table

Venn diagrams correspond to truth tables for the propositions , , etc., in the sense that each region of Venn diagram corresponds to one row of the truth table.[12][13] Another way of representing sets is with R-Diagrams.

See also

Notes

  1. In Euler's Lettres à une princesse d'Allemagne sur divers sujets de physique et de philosophie [Letters to a German Princess on various physical and philosophical subjects] (Saint Petersburg, Russia: l'Academie Impériale des Sciences, 1768), volume 2, pages 95-126. In Venn's article, however, he suggests that the diagrammatic idea predates Euler, and is attributable to Christian Weise or Johann Christian Lange (in Lange's book Nucleus Logicae Weisianae (1712)).

References

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  7. Strategies for Reading Comprehension Venn Diagrams
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Further reading

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External links

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